Ok, adding forum layouts is actually possible, for they who do not know what that is:
A layout is a special un-moveable background and scroller.
For some good layouts, go to http://hotfreelayouts.com
Create a own closed forum for it, and paste the embed- code in the forum description, after you've saved the "layout- forum" you shall edit it again and remove the forum title.
Now, your forum will look a whole lot better, don't you think?
Some layouts may not fit in, but you could always explore the hotfreelayout site and add, and remove them to find the one you like the most.